PERFORMANCE CHARACTERISTICS OF SINGLE-STAGE STEAM JET EJECTORS USING TWO SIMPLE MODELS

Two simple models, one of Hougen, Watson and Ragatz (HWR) and the other by Dotterweich and Mooney (DM), are used to compute the motive steam requirements of single-stage steam jet ejectors. Non-idealities associated with the performance of nozzle, diffuser and that of mixing process are accounted for by nozzle and diffuser efficiency factors. Nozzle and diffuser efficiencies between 0.7-0.9 and 0,75-1.0 respectively, are studied for systems, steam-water vapor, steam-air, and steam-hydrocarbons (n-paraffins: C₁ to C₅). The results are compared with the empirical correlations of Power and Ludwig. In addition, the effect of motive steam pressure on steam consumption is investigated. It is found that predicted steam consumptions, when DM model is employed, agree closely with literature data. It is suggested that model predicted values, rather than the empirical plots, be used in any specific case, since empirical correlations represent only averaged values.